I partially disagree. At least with the terminology.
What does "Post PC" mean? The fact is that now your phone is a "PC". More than "Post PC", we are in the era of "Pervasive PC".
Said that, I believe that in the world there is still space for conventional computers. Both the client devices and the servers hosting the services need to be programmed somehow. You do not want call it "PC"? More than welcome, let's call it "Workstation" then.
Moreove, I do not believe that people doing CAD will move to tablets and touch-screens anytime soon: they still need large monitors and a precise pointing device (and fingers are not).
On the other hand, I think that everything that my mom needs is a tablet to do whatever she does with a PC today. I.e., writing some emails, reading recipes and checking what other people are doing on Facebook.
To go back to the point of your post, many things are "dead" reading the blogs these days: minframes are dead, fortran is dead and even C is dead (in the words of a friend of mine). They are not. They just represent a smaller slice of the market and they work *very* well in their niche. The fact that the market share of these products is smaller is not due to the fact that less people use them, but just a lot people more use other (newer?) technologies. The number of Fortran programmers did not decrease with time, there are just more PHP programmers around.

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